1. Field of the Invention
This invention concerns shaft drive circular blade saws. More particularly, it concerns blades and arbor adaptors for use on different saws with specialized configuration blade mounting arbors.
2. Description of the Prior Art
Circular saws as used herein are those saws having a power source such as an electric or pneumatic motor or gasoline engine which, through a shaft, rotate a generally planar circular blade to cut a kerf. The circular saws may be hand held or mounted on a wheeled carriage or the like, and may cut wood, metal, masonry or other materials. To that end, a number of different saws have been developed which are particularly adapted to for cutting different materials, and blades have been designed for a particular type of cut to be made. For example, smaller hand-held saws have been developed for trim carpentry or metalworking use, larger saws for framing carpentry, and still larger saws mounted on wheeled carriages for use in cutting concrete. The blades for these applications are very different, with tooth patterns varying for metalworking on different metals, cross-cut and rip-cutting of different woods, and abrasive tipped and different toothed blades for cutting concrete or other masonry.
Such circular saws may mount the blade to the shaft by use of an arbor. The motor or other power source turns the shaft and the arbor is rotatably coupled to the shaft. The blade then mounts on the arbor and is held in place by a retaining bolt threadably received in the arbor. A saw may be developed with an arbor having a blade mount with a specific configuration rather than a conventional round mount, e.g. square, diamond-shaped, triangular, etc. In such circumstances, the blade must be configured to with an opening which matches the mount. One approach to this problem in the past has been to provide a blade with has a central round opening common to many saws and a frangible insert which may be removed to permit mounting on a particular saw. While this has been useful in some circumstances, it does not provide for use with arbors having blade mounts of yet further different configurations. Moreover, in heavy duty applications, it risks weakening the blade when the opening for the removable insert has sharp corners. In addition, some larger blades require additional support to provide sufficient torque transmission to avoid blade slippage.
Some prior art saws have employed an arbor or shaft which includes a threaded stud which is threadably received in the arbor or shaft and displaced from the axis of rotation so as to be off-center. This in turn has required a saw blade which has a mounting hole similarly displaced from the center of the saw blade in order to be usable and function by rotating without oscillating. Such an arrangement severely limits the availability of different blades which may be used with the saw when so configured and leads to increased costs of operation.
There has thus arisen a need for a simple and rugged arbor adaptor which permits the use of non-specific saw blades with several circular saws, yet provides sufficient support and strength.
These needs have largely been met by the arbor adaptor and circular saw blade of the present invention. That is to say, the present invention enables the use of a saw blade having a central opening able to mount on an arbor or shaft of circular saws of multiple different applications. As a result, a common and simple saw blade configuration can be used with saws have particular shaped arbors without the necessity of making specialized and custom blades.
The arbor adaptor hereof broadly includes a central aperture and a first engagement side, the first engagement side including a central recess for receiving a non-circular mounting lug of an arbor therein. The first engagement side further includes an annular blade-locating ring which extends normally from the central recess and is configured to radially surround the mounting lug and in turn to receive thereon in radially surrounding relationship the inner margin of the blade which is preferably complementally sized with the outer rim of the blade locating ring. A friction surface is provided radially outwardly of the blade locating ring for clamping the blade to the arbor.
In some embodiments, a second engagement side may be provided for mounting a blade to a second arbor having a differently sized or configured mounting lug, or no mounting lug. The second engagement side includes a second central recess having a different diameter than the central recess of the first engagement side, and a second friction surface. The second friction surface may have a different radially size or dimension than the friction surface on the first side, or the same dimension.
In other embodiments, particularly those where larger diameter blades having greater drive requirements are used, the arbor adaptor may be provided with a drive pin, and the central recess may be defined by an irregular inner rim on the blade locating ring to provide engagement points for contacting the mounting lug. The blade is provided with a complemental drive hole for receiving the drive pin therein, with the mounting lug engaging at least one and preferably at least two engagement points for rotatably driving the arbor adaptor, which throughout the pin and the frictional clamping relationship drives the blade.
A further embodiment of the foregoing invention utilizes an arbor adapter for mounting on saws having an arbor or shaft with an offset stud or a central bore receiving another threaded fastener, thereby enabling the use of a saw blade with an axially centered mounting opening, such as a preferably generally circular inner margin. The arbor adaptor has a central aperture which is offset from the axis of rotation the same displacement as the stud, and has a blade positioning ring which is, as above, centered on the axis of rotation. The outer margin of the arbor adaptor may be generally circular as described above, so that during rotation, the arbor adaptor and blade rotate about the axis of rotation, rather than have an eccentric pattern of motion. Thus, the rotation of the stud, offset to the axis of rotation, causes the central aperture of the arbor adaptor to rotate about the axis of rotation, but the arbor adaptor itself and the blade carried thereby rotate substantially without eccentricity. The weight of the arbor adaptor is generally sufficient to compensate for the slight offset to the central opening. If the stud is provided with a flat side or other change in shape, the central aperture may be provided with a complimentary shape.
These and other advantages will be readily appreciated by those skilled in the art with reference to the following description of the preferred embodiments.